A transmitter will normally comprise at least one amplifier, the efficiency of which can be enhanced by means of pulsed modulation, i.e. mapping of the modulated communication signal to the characteristics of a pulse train, such as, for example, duration, position or density. In such a transmitter, the pulses are used as input to the amplifier. The purpose of driving the amplifier with a pulse train is to make the amplifier operate more of the time at its high efficiency operating points. By using a pulse train, the power amplifier is only operated in one of two highly efficient regions; deep compression or completely off.
However, pulse modulation schemes such as the one described above will introduce undesired signal distortion caused by quantization noise when generating the pulses, which needs to be handled by means of a bandpass filter, a so called reconstruction filter. Due to the nature of the quantization noise, narrowband filters are needed in order to reconstruct the signal before transmitting. These types of filters have a large insertion loss at microwave frequencies, which leads to increased power dissipation in the filter, thus reducing the power efficiency of the transmitter.
Document WO 2006/110590 discloses a power control module which receives a dynamic power control signal, and generates a differential bias signal which is proportional to the dynamic power control signal.